Whisk together the lemon juice, garlic, salt, and pepper. Slowly drizzle in the olive oil, whisking constantly. Set aside.
Peel off any dirty outer leaves from each of your romaine hearts. Cut each one down the middle. I find it's easiest to cut down the middle of the stem first, then cut through all the leaves. Some leaves may fall out - that's okay! Save them for later and you can toss them back into your salad right before serving. (Rinse the leaves if you like and drain cut-side-down on a paper towel. Pat dry before continuing.)
Preheat the grill to medium high. Place hearts of romaine, cut side up, on a plate or rimmed baking sheet. Drizzle with 1 Tbs olive oil. Grill for just a couple minutes, or until leaves are slightly charred. You're not trying to cook the lettuce, just give it some color and smoky flavor.
To serve, place one romaine heart half on a plate, cut side up. Drizzle with dressing, top with cherry tomatoes, Kalamata olives, cucumber, and feta. Sprinkle with dried oregano and extra salt and pepper if desired.