Zest one orange, and reserve zest (2 teaspoons). Cut peel and pith away from both oranges. Use a paring knife to cut out the segments, letting them fall into a bowl, along with the juice.
Add strawberries, sliced fennel, orange zest, and fennel fronds to the bowl of orange segments and toss together gently. Stir in the lemon juice and olive oil, and season with salt and pepper. Add lettuce, toss, and serve.