At what point in reading development does literacy impact object recognition and orientation processing? Is it specific to mirror images? To answer these questions, forty‐six 5‐ to 7‐year‐old preschoolers and first graders performed two same–different tasks differing in the matching criterion‐orientation‐based versus shape‐based (orientation independent)‐on geometric shapes and letters. On orientation‐based judgments, first graders outperformed preschoolers who had the strongest difficulty with mirrored pairs. On shape‐based judgments, first graders were slower for mirrored than identical pairs, and even slower than preschoolers. This mirror cost emerged with letter knowledge. Only first graders presented worse shape‐based judgments for mirrored and rotated pairs of reversible (e.g., b‐d; b‐q) than nonreversible (e.g., e‐ә) letters, indicating readers’ difficulty in ignoring orientation contrasts relevant to letters.