American Airlines, British Airways, and Iberia have round-trip flights from Chicago (ORD) to Brussels, Edinburgh, Frankfurt, or Munich (BRU/EDI/FRA/MUC) for $299-$417 with a connection. Flights October to March. No Weekends.
Note: New Years Eve is available if you can do a 10-day stay or longer.
Note: Carry-on bag is allowed for free on American Airlines, British Airways, and Iberia. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.