Main Street Research LLC
SEC Form 13F institutional filer · CIK 0001513211
13F-HR · 113 reported holdings · 2026-03-31
SEC-registered institutional investment manager.
Reported long-US-equity value
$1.16B
Top-10 concentration
59.7%
Main Street Research LLC — $1.16B AUM allocation strategy
Main Street Research LLC files SEC Form 13F and reports $1.16B of long US equity value across 113 reported holdings for 2026-03-31.
Its largest sector bet is Information Technology 42.0%, followed by Communication Services 11.2% and Consumer Staples 9.5%.
The top 10 holdings account for 60% of reported value — a conviction-weighted book concentrated in its best ideas. The sector and industry splits below are of the same reported value. Track quarter-over-quarter adds, trims, new positions and exits below — sourced from SEC 13F filings, public domain.
Main Street Research LLC — latest SEC 13F insights
Reported long-US-equity value (13F AUM)
$1.16B
total across 113 reported holdings · 2026-03-31 · excludes shorts, cash, non-US
Top-10 concentration
60% of value
higher = narrower conviction; lower = spread / hedging
Biggest adds (shares)
+$AAPL +113K sh · +$23.3M+$MU +104K sh · +$35.3M+$WFC +27K sh · +$1.88M
Biggest trims (shares)
−$HOOD −529K sh · −$60M−$UBER −435K sh · −$35.7M−$PLTR −273K sh · −$53.7M
Exited to nil (held last quarter, gone now)
$BKNG ($20.4M last qtr)$TRMB ($295K last qtr)$LIN ($256K last qtr)$IBM ($251K last qtr)$GILD ($224K last qtr)
Sector allocation (share of reported value)
each slice is a share of the reported long-US-equity value — smaller sectors and the rest of the book roll into “Other holdings”
Qtr shift = share-point change vs the prior quarter's filing — first period tracked for this filer; the column fills in with the next quarterly refresh.
Industry allocation (share of reported value)
- Semiconductors18.2%—
- Interactive Media & Services11.2%—
- Technology Hardware, Storage & Peripherals8.8%—
- Electronic Components7.8%—
- Consumer Staples Merchandise Retail7.6%—
- Diversified Banks5.7%—
- Health Care Distributors5.0%—
- Broadline Retail4.9%—
- Other holdings30.7%—
the finer GICS cut of the same book — same denominator — smaller industries roll into “Other holdings”
Qtr shift = share-point change vs the prior quarter's filing — first period tracked for this filer; the column fills in with the next quarterly refresh.
Top S&P 500 holdings
10 of 10 rows · sorted by Value ↓
| Ticker | Holding | Shares | Value | Δ QoQ | Weight |
|---|---|---|---|---|---|
| $NVDA | NVIDIA Corporation | 621K | $108M | +24.9K | 9.4% |
| $AAPL | Apple Inc | 404K | $102M | +113K | 8.9% |
| $GOOG | Alphabet Inc. Class C Capital Stock | 312K | $89.7M | +14.2K | 7.7% |
| $JPM | JP Morgan Chase & Co | 224K | $65.8M | +1.84K | 5.7% |
| $AVGO | Broadcom Inc | 212K | $65.7M | +7.01K | 5.7% |
| $MCK | McKesson Corporation | 67.8K | $58.6M | +413 | 5.1% |
| $AMZN | Amazon.com Inc | 269K | $56.1M | +9.34K | 4.8% |
| $GLW | Corning Incorporated | 388K | $52.7M | — | 4.6% |
| $COST | Costco Wholesale Corporation | 46.1K | $46M | -16.2K | 4.0% |
| $JNJ | Johnson & Johnson | 187K | $45.7M | +7.56K | 3.9% |
…and 103 more holdings in the full 13F filing (top positions only shown).
SEC Form 13F data sets · public domain · 45-day filing lag · >$100M AUM managers · as reported
← All 13F filers·← QuantOrb.pro
How to read Δ QoQ — the five insight categories, and the caveats
The categories. Analysts, quants and retail traders look past total portfolio value to isolate actionable signals. Five categories matter.
Conviction & concentration shifts
New positions vs complete exits — a brand-new stock signals high conviction; a full liquidation suggests a broken thesis or tax-loss harvesting. Aggressive sizing — look at share count, not dollars: a 20% share increase during a drawdown is strong dip-buying. Concentration — a narrowing top-5/10 means conviction; spreading capital across more names means hedging.
Sector & macro allocation rotations
Aggregating Δ QoQ moves across sectors shows where smart money is leaning in or sneaking out — rotating out of growth into defensives or energy, for example. The fund's total long equity exposure quarter-over-quarter is a proxy for overall institutional risk appetite.
Crowding & smart-money consensus
When several managers initiate or expand the same stock in the same quarter, that is institutional consensus. Contrarian reads: top pickers buying hard into a beaten-down name the market is selling.
Derivative & option overlays
Reported call/put changes indicate whether managers are adding downside hedges or leveraging upside exposure. Note: a long increase may be half of a market-neutral pair trade.
Who reads this
| Retail "cloners" | High-conviction ideas to replicate ~45 days after quarter-end. |
| Corporate IR | Which funds bought or dumped the stock, before the next call. |
| Quant / algo traders | Cross-sectional factor inputs: flow, momentum, ownership. |
Four caveats before you trade on it
- 45-day lag — holdings are quarter-end; positions may already be closed.
- Long-only — 13Fs miss shorts, pair trades and cash.
- No non-US / fixed income — the picture is US equities plus options.
- Corporate actions — splits and spinoffs distort raw share deltas.
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